Michael Louis Demeo, 80, has been missing since 9:30 a.m. Thursday

DELRAY BEACH — Police are continuing their search for a man who went missing Thursday morning after leaving for a doctor's appointment in nearby Boynton Beach.

Michael Louis Demeo, 80, never showed up for the appointment and police have since issued a Silver Alert for him.

Police say Demeo has recently experienced diminished mental capacity and investigators believe he may be wandering throughout Florida, unable to find his way home.

Credit card records show the Demeo purchased gasoline in the Key Largo area of the Florida Keys about 5 a.m. Friday, according to police. His credit card transactions Thursday were traced to Jupiter, Bradenton and Okeechobee.

Police also traced a phone call Demeo made to his home Thursday night to the 407 area code. The phone connection was poor and the call disconnected, police said.

Demeo needs oxygen because of lung cancer issues and has a known heart condition. According to police, he is not carrying money and may not know when to stop for food or other personal needs.

Demeo is driving a 2005 gold and beige Dodge Caravan with a Florida tag S20 3IV.

Police ask that anyone with information on Demeo's whereabouts to contact their local law enforcement agency or the Delray Beach Police Department at (561) 243-7800.